I ran into a situation today where I needed to diff files on a remote server against the ones on a local server when the only connection method I had to connect to the remote server was FTP. I wrote a little quick and dirty script to diff files over FTP. It's stupid simple - it downloads the file and runs diff on it against a local file, outputting the result.
It's great for finding changes on a webhost that cripples real developers by only offering FTP. It's also a great companion to ftpsync, which apes some of the functionality of rsync, again on crippled webhosts.
The command format is:
ftpdiff <local file> <username:[email protected]:/path/to/file>